Current limiting circuit breaker with electrodynamic compensation



Dec. 22, 1970 a. BLANC-TAILLEUR CURRENT LIMITING CIRCUIT BREAKER WITHELECTRODYNAMIC COMPENSATION 7 Sheets-Sheet 1 Filed June 17, 1969 Dec.22, 1970 G. BLANC-TAILLEUR CURRENT LIMITING CIRCUIT BREAKER WITH 7Sheets-Sheet 2 ELECTRODYNAMIC COMPENSATION Filed June 17, 1969 Dec. 22,1970 s. BLANC-TAILLEUR 3,556,949

CURRENT LIMITING CIRCUIT BREAKER WITH ELECTRODYNAMIC COMPENSATION 7Sheets-Sheet '5 Filed June 17, 1969 Fig.9

T g g G. BLANC-TAILLEUR 3,550,049 CURRENT LIMITING C Dec. 22, 1970IRCUIT BREAKER WITH ELECTRODYNAMIC COMPENSATION 7 Sheets-Sheet 4.

Filed Jun 17, 1969 Fig/l0 Dem 22, 1970 G. BLANC-TAILLEUR 3,550,049

CURRENT LIMITING CIRCUIT BREAKER WITH ELECTRODYNAMIC COMPENSATION FiledJune 17, 1969 7 Sheets-Sheet 5 Fig 11 Dec. 22, 1970 G. BLANC-TAILLEUR3,550,049

CURRENT LIMITING CIRCUIT BREAKER WITH ELECTRODYNAMIC COMPENSATION FiledJune 17, 1969 7 Sheets-Sheet 6 Dec. 22, 1970 G. BLA NC-TAILLEUR3,550,049

CURRENT LIMITING CIRCUIT BREAKER WITH ELECTRODYNAMIC COMPENSATION 7Sheets-Sheet 7 Filed June 17, 1969 United States Patent 3,550,049CURRENT LIMITING CIRCUIT BREAKER WITH ELECTRODYNAMIC COMPENSATION GuyBlanc-Tailleur, Seyssins, France, assignor to Merlin Gerin, SocieteAnonyme, Grenoble, France Filed June 17, 1969, Ser. No. 833,922 Claimspriority, application 3France, July 5, 1968,

Int. on. Him 77/10 U.S. Cl. 335-195 12 Claims ABSTRACT OF THE DISCLOSURECurrent limiting circuit breakers are known. In these apparatus, thepath of the current which passes between the closed contacts forms aloop and the electrodynamic forces due to the current in the loop tendto open the movable contacts against the opposing force of the contactpressure biasing springs. In case of short-circuit or of substantialovercurrent, these electrodynamic forces overcome this opposing forceand the repulsion of the contacts then makes it possible to obtain arelatively sudden separation of the contacts and the formation of an arewhich increases in length to introduce an increasing im; pedance in thecircuit, causing a limiting of the current. This automatic opening ofthe contacts is reversible until the tripping device of the circuitbreaker, which is generally an electromagnetic tripping device but whichmay also be an electrodynamic tripping device, gives a positive orderfor the opening of all the poles of the apparatus, unlocking the movablecontacts. This control order is given as a function of the instantaneousvalue of the current when the latter increases above a predeterminedvalue, regardless of the relative position of the contacts which havebeen separated by the said electrodynamic forces. The repulsion actionof the contacts is practically instantaneous but the unlocking whichresults from the action of the tripping device is delayed by theintervention of inertia, hysteresis phenomena, etc. Preciousmilliseconds elapse between the start of the automatic electrodynamicopening of the contacts against the contact springs and the actualunlocking of the movable contacts. The automatic opening of the contactsmay be hesitant, in particular when the overcurrent is close to thelimit value which causes said automatic opening, or when the substantialcurrent decreases in its cycle (or alternation). Weldings and wear ofthe contacts then occur, making the apparatus unusable sooner or later.

Furthermore an overcurrent of lower value which is incapable of causingthe automatic opening of the contacts nevertheless produces a decreasein the contact pressure which also may lead to an excessive heating ofthe contact studs.

In order to improve this behavior of closed limiting circuit breakers,it has been proposed to introduce into these current-limiting deviceswith automatic electrodynamic opening an electrodynamic compensationwhich operates when tthe device is in its normal closed position. FrenchPat. 1,316,904 shows such a device in which a dividing of the maincontacts makes it possible to divide the current passing through theclosed contacts into two parallel branches so as to produce anelectrodynamic force which tends to increase the pressure of the closedcontacts against the opposing force of repulsion which leads to theautomatic opening. In order to make the transition between thecompensated condition in closed state of the circuit breaker and thenoncompensated condition which causes the automatic opening withlimitation of the current, the movable contact executes a swingingmovement to open a pair of main contacts to close the arcing contactsand then to open the other pair of main contacts, thus destroying thecompensation as a result of the geometric configuration of theconductive parts in question.

In these known devices, the swinging movement of the movable contact iscaused by a special electromagnetic or electrodynamic tripping devicewhich intervenes in the mechanical control of the movable contact,resulting in a delayed action which makes the automatic openingproblematical. Furthermore, in this known device, the flexible conductorfor the feeding of the current to the movable contacts always acts inthe sense of destroying the compensation, thus also making thecompensation problematical, even in the closed position of the two pairsof main contacts.

An object of the present invention is an improvement in circuit breakersallowing a definite instantaneous automatic transition from thecompensated state to the automatic-opening state without the use ofspecial tripping devices and without recourse to subdividing of the maincontacts.

Automatic unlocking of a movable contact support member under the actionof electrodynamic forces is known from French Pat. 1,275 ,-25 5, but ina version which does not have electrodynamic compensation and in whichfurthermore the arcing contacts and the main contacts are all closed inthe normal closed circuit position of the device.

Another object of the invention is to provide automatic unlocking of themovable contact members of a circuit breaker having electrodynamiccompensated closed contacts. Still another object of the invention is toprovide an electrodynamic compensated circuit breaker of a simple andeconomical design having poles which open automatically and individuallytowards their normal opening position without intervening of the normaltripping device.

Still another object of the invention is a circuit breaker in which thecontacts are electrodynamically compensated until the very moment oftheir separation, from which moment on the electrodynamic forces causethe rapid opening of the contacts.

Other characteristics and advantages will be clear from the followingdescription of several embodiments of the invention, which are shown inthe accompanying drawings in which:

FIG. 1 is a schematic side view illustrating the principle of a knowncontact device with electrodynamic compensation, the device being shownin its normal closed circuit position;

FIG. 2 shows the same device at the start of its opening stroke underthe action of the electrodynamic forces;

FIG. 3 shows the device of FIGS. 1 and 2 after the intervention of thetripping device;

FIG. 4 shows schematically, in side view, a contact device according tothe invention in its normal closed circuit position;

FIG. 5 shows this device of the invention as it is just about to unlock;

FIG. 6 shows the device of FIGS. 4 and 5 just after unlocking at thetime when the arcing contacts touch each other and then immediatelyseparate in order to establish an arc;

FIG. 7 shows this device at the end of the opening stroke caused by theelectrodynamic forces;

FIG. 8 shows this device at the end of the opening stroke after theactuation of the tripping device (not shown);

FIGS. 9, 10, l1, l2 and 13 shows, in side view and partially in section,a practical embodiment of a compensated limiting circuit breakeraccording to the invention, these figures corresponding to FIGS. 4, 5,6, 7 and 8 respectively.

FIGS. 14 to 17 show schematically in side view the principle of anotherembodiment, the different posi tions corresponding to those of FIGS. 4,.5, 6 and 7 respectively.

In FIGS. 1 to 3 which illustrate a known contact device, a movablecontact supporting arm 10 is connected by its end 12 to a connection bar14 by means of a flexible conductor or strap 16 arranged in the form ofa loop. The upper portion of the arm 10 bears a main contact stud 18 andtowards the top an arcing contact stud 20, which contact studs cooperatewith the main stationary contact stud 22 and the arcing contact stud 24respectively which are disposed on a stationary contact support member25 which is connected to the other connecting bar 26. The arm 10 ispivotally mounted by means of a lug 27 on a pin 28 borne by a supportmember 30 which in its turn is pivoted on a fixed pin 32. The pin 28 isarranged between the end 12 and the upper part of the contact arm 10 anda compression spring 33 which brings the contacts together acts on theend 12, its other end resting against a stationary surface 35. Theopening and closing of the contacts is effected by a rotary drive shaft34, one crank 36 of which is pivoted at 37 on an insulating connectingrod 38, the other end of which is articulated at 39 to an arm 40 whichis rigidly connected with the support 30.

In closed position of the main contacts 18, 22 shown in FIG. 1, thesupport member 30 and the pin 28 are locked by the rod links 36 to 40and. the spring 33 urges the arm 10 in rotation around the pin 28applying the movable main contact 18 against the stationary main contact22. The arcing contacts 20, 24 are spaced apart and the assembly isgeometrically arranged in such a manner that the electrodynamic forcesof repulsion of the contacts 18, 22 are compensated for by theelectrodynamic forces produced in the loop 16. This compensationmaintains sufiicient contact pressure for any value of current.

The opening of the contacts takes place by rotation of the drive shaft34 in anti-clockwise direction which is caused by a tripping device (notshown) which permits the displacement of the pins 37, 39 and 28 andthereby unlocks the support 30. Under the action of the forces which areapplied to it by the arm 10, Le. the resultant of the electrodynamicforces of repulsion of the contacts and loop and the force of the spring33, the pin 28 moves, liberating the arm 10 which then pivots around themain contact 22 until the arcing contacts 20, 24 touch (see FIG. 2) andthe main contacts are subsequently separated. The compensation effect isdestroyed by the spatial position of the arcing contacts and the arm 10is then suddenly pushed back towards the open circuit position shown inFIG. 3.

In the following figures, the same reference numbers are employed todesignate parts similar or identical to those shown in FIG. 1, and theseparts Will not be described again in detail below.

In FIGS. 4 to 13 which illustrate a first embodiment of the invention,the electrical circuit of the pole is identical to that of FIGS. 1 to 3,as is the mounting of the contact arm 10 by a pin 28 on a support 30-which is articulated at 32. The support 30 has an arm 46 the end ofwhich cooperates with a locking device consisting in the exampleselected of two rollers 48 and 50 cooperating with a stop 52 which isintegral with the arm 46. The roller 48 is borne by the end of said arm46 and the roller 50 by the end of a lever 54 which is pivoted at 39 tothe end of the operating rod 38. Between the pins 39 and 32 is inserteda knuckle joint comprising two toggle levers 60', 62 pivoted at 58, theopposite ends of which are pivoted at 39 and 32 respectively. An elasticbiasing force, produced by compression spring 64 which rests at its endsagainst a lug 66 of the lever 62 and against the lever 60 respectively,tends to stretch the knuckle joint. The end of a trip rod 70 which isrigidly connected with the locking lever 54 is arranged opposite and asmall distance from the element 66 of the lever 62 so that upon abending of the knuckle joint 58 having levers 60, 62, against the actionof the spring 64, it comes against and is acted upon by the element 66,causing the releasing of the locking device 50, 48 by pivoting inanticlockwise directions of the lever 54 around the pin 39 and thereforethe unlocking of the support 30 and the release of the pole. A slot 72in the lever 54 (see FIG. 9) limits the swinging movement of the lockinglever 54 in both directions with respect to the pin 58 which passesthrough it. A stop 31 which is rigidly connected with the arm 30 limitsthe pivoting of the arm 10 around the pin 28 and a fixed stop 71arranged on the stationary side plate 73 receives the roller 28 of thepin 28 at the end of the stroke (see FIGS. 12 and 13).

The contact device of FIGS. 4 to 8 and 9 to 13 respectively operates asfollows:

In the closed and locked position shown in FIGS. 4 and 9, the support 30and the arm 46 are urged in rotation around the pin 32 by theelectrodynamic forces which are transmitted by the pin 28 in clockwisedirection. These forces are also transmitted by the locking device 48,50 and the lever 54 to the pin 39 whose displacement, by pivoting of theconnecting rod 38, is opposed by the knuckle joint 60, 58, 62, 66, 64.The sup port 30 and the pin 28 are thus locked, the contacts beingcompensated by the effect of the loop 16, as in the example of FIG. 1.The spring 64 of the knuckle joint 58 is subjected to a compressiveforce which is proportional to said forces transmitted by the pin 28 tothe support 30.

Upon overcurrent or a short-circuit current, the electrodynamic forcesacting on the arm 10 increase as well as the reaction on the pin 28 andtherefore on the spring 64, which yields, causing a bending of theknuckle joint 62, 60 until the trip rod 70 and the part 66 abut, andfrom this moment the rod 70 starts to pivot the lever 54 in theanticlockwise direction, in a first stage until the centers of the pins39, 48 and 50 are aligned. The slight pivoting of the support 30 and theslight translation thus created of the pin 28 towards the right on thefigures involves a swinging of the arm 10 in the anti-clockwisedirection, decreasing the distance between the arcing contacts 20, 24without the latter, however, coming into contact, the main contactsserving as a pivot without separating.

If the overcurrent does not exceed a predetermined limit whichcorresponds to the position of the members in accordance with FIGS. 5and 10 or if this overcurrent disappears before the tripping proper, thedifferent parts are automatically returned to their initial position,shown in FIGS 4 and 9, under the action of the diiferent elastic forcesand in particular of a tension spring 74 which pulls the lever 54 backtowards the arm 66. The contact pressure will not have decreased duringthis entire period.

If the overcurrent increases, the element 66 of the knuckle joint pushesthe trip rod 70 and releases the roller 48 from the roller 50 (see FIGS.6 and 11). The support 30 is then entirely free and swings, the openingof the circuit breaker taking place by the coming into contact with eachother of the arcing contacts 20, 24, followed by the separation of themain contacts 18, 22 with rupture of the electrodynamic compensation andby rapid separation of the arcing contacts (see FIGS. 7 and 12). Thisopening is obtained in powerful manner as a result of the electrodynamicforces of repulsion between the contacts, the compensation being nowentirely de stroyed, and also as a result of the contact pressure spring33, since the pin 28 has been freed. The roller 28 of the pin 28 comesagainst the part 71 and the arm 10 comes against the stop 31.

The locking lever 54 which is stopped by the striking of the left end ofthe slot 72 against the pin 28 can cause at the end of its stroke thetripping of the conventional automatic opening mechanism (consisting ofa tripping device not shown) of all the poles, causing the rotation ofthe drive shaft 34 in suitable manner. This results in a displacement ofthe opening rod 38 which returns the lever 54 into reset position bymeans of the spring 74, ready for another operation (see FIGS. 8 and13). Upon the closing movement which is controlled by the connecting rod38, the locking lever 54, arm 46 and knuckle joint 60, 62 constitutepractically a rigid assembly which brings the contact arm 10 into closedposition. This is also true upon a normal opening operation (manual orby tripping device) during which the parts are brought from the positionshown in FIGS. 4 and 9 to the position shown in FIGS. 8 and 13 bydisplacement of the connecting rod 38 without the opening of the catch48, 50.

Another embodiment of the invention is illustrated in FIGS. 14 to 17 inwhich again the pole comprises the support 30 as well as the drive orcontrol shaft 34. The

connecting rod 38 of FIGS. 4 to 8 is connected to the pin 39 by aninterlock mechanism which comprises a hollow housing 76 rigidlyconnected with the connecting rod 38 and having a step at 78 leading toa cavity 80. A spring :82 is guided so that it is contained along theextension of a rod 84 which is pivoted at 39. A guide cage 86 of thespring 82 has an inclined plane 88 which cooperates with a stop 90. Thecompression spring 82 rests against the rod 84, on the one end, andagainst a lock 92, on the other end. In closed circuit position (seeFIG. 14), the lock 92 rests against the step 78. The compression of thespring 82 and the moving together of the parts 38, 84 bring the inclinedplane 88 in contact with the stop 90, a continuation of the movementunder the action of the electrodynamic forces causing a swinging of theelement 82 with respect to the element 7-6 causing at a given moment thedisengagement between the look 92 and the step 78 and the opening of thepole, the lock 92 coming into the cavity 80.

'It is easy to see that the operation of the device of FIGS. 14 to 17 issimilar to that of FIGS. 4 to 13. In order to follow the course of thetripping, compare FIGS. 14 to 17 with FIGS. 4 to 8 respectively. Thetripping of the other poles which have not been automatically trippedindividually (a single pole is shown in the figures) is brought about bythe pivoting of the connecting rod 36 in anti-clockwise direction andresets the lock 92 in front of its step 78 after having effected acertain compression of the spring 82 which was relaxed during thetripping due to the lefthand wall of the housing 76 which rests againstthe lefthand end of the spring 82.

What is claimed is:

1. A circuit breaker comprising an elongated movable contact arm, amovable contact member mounted on a first end portion of said contactarm and cooperating with a relatively stationary contact member,conducting current supply means connected to a second end portion ofsaid contact arm, said conducting means forming part of a current loop,said contact members in their normal closed circuit position being urgedtogether by electrodynamic forces due to currents flowing in said loop,a movable support member for said contact arm, bias means forelastically biasing said support member towards its normal closedcircuit position, releasable locking means to confine the movement ofsaid support member between its said normal closed circuit position anda predetermined intermediate position in opening direction, and controlmeans to release said locking means and adapted to be operated by saidsupport member substantially in its said intermediate position to causethe unlocking of said support member and the opening of said circuitbreaker, whereby said electrodynamic forces urge said contact armtowards its open circuit position after unlocking of said supportmember.

2. A circuit breaker according to claim 1, wherein said contact arm ispivotably mounted on said support member intermediate said end portions.

3. A circuit breaker according to claim 1, wherein said support memberis pivotably mounted on a fixed axis.

4. A circuit breaker according to claim 1, wherein said bias meanscomprise spring means, said control means comprising abutment meansabutting upon a predetermined straining of said spring means.

5. A circuit breaker according to claim 4, wherein said control meanscomprise a toggle lever stressed by said spring means.

6. A circuit breaker according to claim 1, wherein said locking meanscomprise a roller.

7. A circuit breaker according to claim 4, wherein said abutment meanscomprise an inclined plane.

8. A circuit breaker according to claim 2, wherein said contact memberscomprise a pair of main contacts and a pair of arcing contacts, saidcontact arm executing a swinging movement between upon unlocking of saidsupport member to sequentially close said arcing contacts, open saidmain contacts and open said arcing contacts.

9. A circuit breaker according to claim 8, wherein said main and arcingcontacts are disposed in position so that said electrodynamic forcesurge said main contacts together until unlocking of said support member.

10. A circuit breaker according to claim 1, wherein said conductingmeans comprise a flexible strap.

11. A circuit breaker comprising a pivotably mounted contact arm, amovable main and a movable arcing contact disposed on said contact armand cooperating respectively with a relatively stationary main and arelatively stationary arcing contact, conducting means to supply currentto said movable main and arcing contacts, said movable and relativelystationary main contacts being urged together in their normal closedcircuit position by electrodynamic forces due to currents flowing insaid conducting means, releasable locking means limiting the pivotalmovement of said contact arm between its normal closed circuit positionand a position intermediate between said normal closed circuit positionand an open circuit position, spring means biasing said contact armtowards said normal closed circuit position, and control means operableby said contact arm to release said locking means and unlock saidcontact arm in said intermediate position causing the momentary closingof said arcing contacts and the opening of said circuit breaker, theopening movement of said contact arm being accelerated by saidelectrodynamic forces.

12. A circuit breaker according to claim 11, further comprisingindependent trip means, the tripping of said trip means causing theresetting of said released locking means before closing of the circuitbreaker.

References Cited UNITED STATES PATENTS 2,839,632 6/1958 Varichon 3351953,238,339 3/1966 Fehling '33516 FOREIGN PATENTS 942,916 6/ 1962 GreatBritain 335-195 262,424 6/1968 Germany 335l6 BERNARD A. GILHEANY,Primary Examiner H. BROOME, Assistant Examiner

